Seat adjustment passenger side

Hello SL Friends Have a problem with the seat adjustment on the passenger side which only goes one side up. When I look up I saw that a plastic cap on the shaft is shaved off. Knows of you someone how to replace this part, possibly with pictures. I could imagine of the the seat must go out. Furthermore, my seat heating on the driver side does not work. Electricity is on the plug, backrest also works. MfG Ernst